In the related art, an image reading device corrects a reading signal using reference values of a white level and a black level. For example, the image reading device creates a reference value of a white level by reading a white reference plate. However, the image reading device in which a position of a reading unit is fixed can perform reading of a reference plate which is provided at a fixed position only at a fixed reading position. An accuracy of a reference value of a white level which is created using a result of reading the reference plate only at a fixed position deteriorates due to an influence of dirt which adheres to the reference plate.
For this reason, in the image reading device in the related art, a mechanism for moving a reading position of a reading unit in the sub-scanning direction is necessary in order to read a white reference plate by a plurality of pixels.